Motorcycles may use either air- or water-cooling to keep engine temperatures at acceptable levels. Air-cooled engines rely on air flowing across the outer surfaces of the engine to provide cooling of the beat generated by combustion. While convection and ambient wind may provide some airflow to aid cooling the engine, air-cooled engines rely on air movement generated by forward motion of the motorcycle to provide the bulk of the cooling effect. In situations where the motorcycle's engine is being run for extended periods of time without forward movement of the motorcycle (for example, when the motorcycle is stuck in traffic), the engine may overheat, damaging the engine. Improvements to the ability to cool air-cooled engines are desirable.
One approach to improved cooling of air-cooled motorcycle engines is to utilize the oil used to lubricate the operation of the engine to also carry some of the heat away from the engine. The oil circulated through the engine comes into contact with engine parts heated by combustion or exhaust gases. As the oil circulates through the engine, the oil filter and the oil pan, some of the heat is dissipated but it is desirable to improve the ability of the oil to dissipate heat before being recirculated through the engine. It is known to direct the heated oil through heat sinks, radiators or other similar structures to improve the ability of the oil to aid in engine cooling.
At the same time, for aesthetic reasons, many motorcyclists prefer not to have an obvious structure, such as a finned radiator or other traditional heat sink, attached to their motorcycle, even though such a structure might perform the desired function. Some of these non-obvious approaches have included circulation of the oil through frame members of the motorcycle or through foot and motor guards. Improvements to the non-obvious structures for aiding the ability of engine oil to cool motorcycle engines are desirable.